Ruthenium Complexes Immobilized on Functionalized Knitted Hypercrosslinked Polymers as Efficient and Recyclable Catalysts for Organic Transformations

Hyper-Cross-Linked Polyphosphines as Nanoporous Macroligands-A Systematic Study on Cross-Linking and Their Catalytic Application in the CO2 Hydrogenation

Hyper-cross-linked polymers (HCPs) enable the tailored synthesis of functionalized materials and provide a versatile design strategy for porous macroligands. Based on the prototypical triphenylphosphine (PPh3) monomer, we investigate the role of the involved cross-linking reagents in the formation of polyphosphines and evaluate structure-activity relations for application in the catalytic CO2 hydrogenation: namely by varying the Friedel-Crafts catalyst, the cross-linker unit and the degree of cross-linking. The study of monomeric reactivities shows that phosphines are insufficiently activated by iron chloride catalyzed cross-linking and that the stronger aluminum chloride is required to ensure PPh3 incorporation. Applying aromatic cross-linker units introduces porosity and promotes the accessibility of ligating centers for the immobilized ruthenium species. The thus formed solid catalysts exhibit excellent performances in the hydrogenation of CO2 to formic acid in the aqueous phase and are studied in successive recycling runs. The partial structural degradation of the frameworks during catalysis is addressed by adjusting higher degrees of cross-linking, leading to an improved stabilization of the catalyst. Overall, this study highlights cross-linking strategies for the tailoring of phosphine-based HCPs and the design of stable macroligands under catalytic conditions.

Directly Knitted Hierarchical Porous Organometallic Polymer-Based Self-Supported Single-Site Catalyst for CO2 Hydrogenation in Water

In recent times, heterogenization of homogeneous molecular catalysts onto various porous solid support structures has attracted significant research focus as a method for combining the advantages of both homogeneous as well as heterogeneous catalysis. The design of highly efficient, structurally robust and reusable heterogenized single-site catalysts for the CO2 hydrogenation reaction is a critical challenge that needs to be accomplished to implement a sustainable and practical CO2 -looped renewable energy cycle. This study demonstrated a heterogenized catalyst [Ir-HCP-(B/TPM)] containing a molecular Ir-abnormal N-heterocyclic carbene (Ir-aNHC) catalyst self-supported by hierarchical porous hyper-crosslinked polymer (HCP), in catalytic hydrogenation of CO2 to inorganic formate (HCO2 - ) salt that is a prospective candidate for direct formate fuel cells (DFFC). By employing this unique and first approach of utilizing a directly knitted HCP-based organometallic single-site catalyst for CO2 -to-HCO2 - in aqueous medium, extremely high activity with a single-run turnover number (TON) up to 50816 was achieved which is the highest so far considering all the heterogeneous catalysts for this reaction in water. Additionally, the catalyst featured excellent reusability furnishing a cumulative TON of 285400 in 10 cycles with just 1.6 % loss in activity per cycle. Overall, the new catalyst displayed attributes that are important for developing tangible catalysts for practical applications.

Total Syntheses of Uncommon C30 Terpenoids: Chamaecydin and Isochamaecydin

(-)-Chamaecydin and (-)-isochamaecydin, two uncommon C30 terpenoids comprising abietane-type diterpenes and thujane-type monoterpenes, were achieved from β-pinene with (-)-sabinene in 18 and 20 steps, respectively. Key steps include a Claisen-Ireland rearrangement to establish the all-carbon quaternary center, a Rh catalyzed C-H bond insertion reaction to install a spiro-five-membered ring and a Lewis acid promoted cyclization of polyenes to construct the two six-membered rings.

A Journey from June 2018 to October 2021 with N,N-Dimethylformamide and N,N-Dimethylacetamide as Reactants

A rich array of reactions occur using N,N-dimethylformamide (DMF) or N,N-dimethylacetamide (DMAc) as reactants, these two amides being able to deliver their own H, C, N, and O atoms for the synthesis of a variety of compounds. This account highlights the literature published since June 2018, completing previous reviews by the author.

Two C═C Bond Participation in Annulation to Pyridines Based on DMF as the Nonadjacent N and C Atom Donors

Two C═C bond participation in annulation to pyridines using N,N-dimethylformamide (DMF) as the N1 and C4 synthons has been carried out. In this reaction, DMF contributed one N atom and one C atom to two disconnected positions of pyridine ring, with no need for an additional nitrogen source. Two C═C bonds in two molecules of substituted styrenes offered four carbon atoms in the presence of iodine and persulfate. With the optimized conditions in hand, both symmetric and unsymmetric diaryl-substituted pyridines were obtained in useful yields. On the basis of relevant literature and a series of control experimental results, a possible mechanism was proposed in this work, which may demonstrate how DMF provides both N1 and C4 sources.

DMSO as a Dual Carbon Synthon and Water as Oxygen Donor for the Construction of 1,3,5-Oxadiazines from Amidines

A selective and efficient synthesis of diaryl 1,3,5-oxadiazines was established for the first time from simple and readily available amidines in wet DMSO. DMSO was employed as a dual carbon synthon and water offered the oxygen atom to construct the oxadiazine ring. The reaction involved two new C-N and two new C-O bond formations.

Ruthenium-Catalyzed Cycloadditions to Form Five-, Six-, and Seven-Membered Rings

Ruthenium-catalyzed cycloadditions to form five-, six-, and seven-membered rings are summarized, including applications in natural product total synthesis. Content is organized by ring size and reaction type. Coverage is limited to processes that involve formation of at least one C-C bond. Processes that are stoichiometric in ruthenium or exploit ruthenium as a Lewis acid (without intervention of organometallic intermediates), ring formations that occur through dehydrogenative condensation-reduction, σ-bond activation-initiated annulations that do not result in net reduction of bond multiplicity, and photochemically promoted ruthenium-catalyzed cycloadditions are not covered.

Palladium supported on triazolyl-functionalized hypercrosslinked polymers as a recyclable catalyst for Suzuki-Miyaura coupling reactions

A novel hypercrosslinked polymers-palladium (HCPs-Pd) catalyst was successfully prepared via the external cross-linking reactions of substituted 1,2,3-triazoles with benzene and formaldehyde dimethyl acetal. The preparation of HCPs-Pd has the advantages of low cost, mild conditions, simple procedure, easy separation and high yield. The catalyst structure and composition were characterized by N2 sorption, TGA, FT-IR, SEM, EDX, TEM, XPS and ICP-AES. The HCPs were found to possess high specific surface area, large micropore volume, chemical and thermal stability, low skeletal bone density and good dispersion for palladium chloride. The catalytic performance of HCPs-Pd was evaluated in Suzuki-Miyaura coupling reactions. The results show that HCPs-Pd is a highly active catalyst for the Suzuki-Miyaura coupling reaction in H2O/EtOH solvent with TON numbers up to 1.66 × 104. The yield of biaryls reached 99%. In this reaction, the catalyst was easily recovered and reused six times without a significant decrease in activity.

Imidazolium-Functionalized Ionic Hypercrosslinked Porous Polymers for Efficient Synthesis of Cyclic Carbonates from Simulated Flue Gas

The rapid growth of CO₂ emissions, especially from power plants, has led to the urgent need to directly capture and fix CO₂ in the flue gas after simple purification rather than energy-intensive gas separation. Herein, imidazolium-functionalized ionic hypercrosslinked porous polymers (HCPs) bearing adjustable surface groups were straightforwardly synthesized through co-hypercrosslinking of benzylimidazole salts and crosslinker through Friedel-Crafts alkylation. Abundant microporosity and relatively high ionic moieties were obtainable in the ethyl-group-tethered ionic HCP, giving a remarkably selective CO₂ capture performance with a CO₂ uptake of 3.05 mmol g^-1 and an ideal adsorbed solution theory (IAST) CO₂ /N₂ selectivity as high as 363 (273 K, 1 bar). This ionic polymer demonstrated high efficiency in the synthesis of cyclic carbonates from the coupling of various epoxides with the simulated flue gas (15 % CO₂ and 85 % N₂ ), giving high yields, large turnover numbers (up to 4800), and stable reusability under additive- and solvent-free conditions.

Sulfoxidation inside a hypercrosslinked microporous network nanotube catalyst

In the present work, a kind of efficient heterogeneous catalyst was synthesized from amine-functionalized hypercrosslinked bottlebrush copolymers of microporous network nanotubes (amine-MNNs) and Na₂WO₄.

Palladium/phosphorus-functionalized porous organic polymer with tunable surface wettability for water-mediated Suzuki–Miyaura coupling reaction

A series of phosphorus-functionalized porous organic polymers supported palladium catalysts with tunable surface wettability were successfully prepared using an easy copolymerization and successive immobilization method. The obtained polymers were carefully characterized by many physicochemical methods. Characterization results suggested that the prepared materials featured hierarchically porous structures, high pore volumes, tunable surface wettability and strong electron-donating ability towards palladium species. We demonstrated the use of these solid catalysts for water-mediated Suzuki–Miyaura coupling reactions. It was found that the surface wettability of the prepared catalysts has an important influence on their catalytic activities. The optimal catalyst, which has excellent amphipathicity and relatively high phosphorus concentration, displayed superior catalytic activity compared to the other catalysts. Under ambient conditions, a variety of aryl chlorides can be efficiently transformed to biaryls in high yields. Moreover, the catalyst could be easily recovered and reused at least six times.

A palladium/phosphorus-functionalized porous organic polymer with tunable surface wettability was successfully prepared. The catalyst displayed high catalytic activity for the water-mediated Suzuki–Miyaura coupling reaction of aryl chlorides.

A step forward in solvent knitting strategies: ruthenium and gold phosphine complex polymerization results in effective heterogenized catalysts

A knitting strategy has been applied to obtain metal–phosphine porous organic polymers (Kphos(M)), resulting in effective heterogenized catalysts for different reactions.

Palladium immobilized on functionalized hypercrosslinked polymers: a highly active and recyclable catalyst for Suzuki–Miyaura coupling reactions in water

Three palladium complexes were synthesized via an external cross-linking reaction and found to be effective heterogeneous catalysts for the Suzuki–Miyaura reaction.

Ultrafine and highly dispersed platinum nanoparticles confined in a triazinyl-containing porous organic polymer for catalytic applications

The fabrication of stable porous organic polymers (POPs) with heteroatoms that can firmly anchor noble metal nanoparticles (NPs) is a challenging and significant task for heterogeneous catalysis. In the current work, we used piperazine and cyanuric chloride as precursors and successfully fabricated a PC-POP material. Then, through the impregnation method and subsequently the reduction method, ultrafine Pt NPs were confined in the PC-POP with a high dispersion. The Pt NP active sites are accessible due to the uniform mesopores of the PC-POP that facilitate diffusion and mass transfer. The organic cages and nitrogen atoms in the PC-POP frameworks can make the Pt NPs stably anchored in the PC-POP during the catalytic process. The obtained Pt@PC-POP nanocatalyst showed excellent catalytic activity and good recyclability in the selective hydrogenation of halogenated nitrobenzenes and catalytic hydrolysis of ammonia borane as compared with many other reported noble metal catalysts.

Acetylene in Organic Synthesis: Recent Progress and New Uses

Recent progress in the leading synthetic applications of acetylene is discussed from the prospect of rapid development and novel opportunities. A diversity of reactions involving the acetylene molecule to carry out vinylation processes, cross-coupling reactions, synthesis of substituted alkynes, preparation of heterocycles and the construction of a number of functionalized molecules with different levels of molecular complexity were recently studied. Of particular importance is the utilization of acetylene in the synthesis of pharmaceutical substances and drugs. The increasing interest in acetylene and its involvement in organic transformations highlights a fascinating renaissance of this simplest alkyne molecule.

Hyper-cross-linked polymer supported rhodium: an effective catalyst for hydrogen evolution from ammonia borane

In situ formation of HCP-PPh₃-Rh and concomitant catalytic AB hydrolysis was performed for efficient hydrogen generation from AB hydrolysis.